/Engine/Source/Runtime/SlateCore/Public/Styling/CoreStyle.h
Note, these sizes are in Slate Units. Slate Units do NOT have to map to pixels.
namespace CoreStyleConstants { const [UE::Slate::FDeprecateVector2DResult](API\Runtime\SlateCore\Types\FDeprecateVector2DResult) CoreStyleConstants::Icon5x16 ( 5. 0f, 16. 0f ) }